Process for manufacturing tight seals, and seals obtained by this process

ABSTRACT

Method of forming gaskets by projecting a layer comprising 7090% of a fibrous material and 10-30% of a settable binder onto a supporting sheet, causing the binder to set, and there compressing the layer. An adhesive may be used to secure the layer to the sheet, or the sheet may be treated to prevent adhesion of the layer and removed after the compression step.

United States Patent [151 3,660,184 Burelle et al. May 2, 1972 [54]PROCESS FOR MANUFACTURING [56] References Cited TIGHT SEALS, AND SEALSOBTAINED BY THIS PROCESS UNITED STATES PATENTS [72] Inventors: PierreBurelle, Le Vesinet; Jean Alfred aq fi 5 2 3 Engelhardt y both of France1c ae son eta 2,577,205 12/1951 Meyer et a1 1 56/622 [73] Assignee:Societe anonyme dite Cefilac, Paris, France 2,951,721 9/1960 A'sp..277/227 X 3,490,115 1/1970 Owens ....156/62.2 X [22] May 19703,352,080 11/1967 Rondum ..156/245 x [21] Appl.N0.: 38,521 3,506,5214/1970 Hullen et al. .....l56/369 2,753,199 7/1956 Victor ..277/233Related US. Application Data [63] Continuation-impart of Ser. No.565,754, July 18, Primary Examiner8enjamin Borche" 1966, abandoned.Assistant Examiner-H. J. Tudor Attorney-Holcombe, Wetherill andBrisebois [30] Foreign Application Priority Data July 29, 1965 France..26541 [57] ABSTRACT Method of forming gaskets by projecting a layercomprising [52] US. Cl ..156/62.2, 1 17/29, 156/369, 70-90% ofa fibrousmaterial and 10-30% ofa settable binder 264/] 277/227 onto a supportingsheet, causing the binder to set, and there [51 Int. Cl. ..B29j 5/02 omressing the layer, An adhesive may be used to secure the [58] Field OfSearch layer to the heet or the heet may be treated to prever" adhe.

sion of the layer and removed after the compression step.

16 Claims, No Drawings PROCESS FOR MANUFACTURING TIGHT SEALS, AND SEALSOBTAINED BY THIS PROCESS This application is a continuation-in-part ofapplicants prior application, Ser. No. 565,754, filed July 18, 1966, nowabandoned.

SUMMARY OF THE INVENTION This invention relates to a method ofmanufacturing sealing members, such as cylinder-head gaskets forinternal combustion engines.

A principal object of the present invention is to provide a simpler andmore economical method than the methods heretofore known formanufacturing such gaskets when the greater part thereof consists of afibrous material.

Another object of the invention is to provide gaskets having propertieswhich are superior to those of comparable gaskets now known. A furtherobject of the invention is to provide a process making it possible tocontrol the thickness of the gasket at all points with great precision,and to correct any variation from that thickness, thus reducing thenumber of gaskets which have to be scrapped. 7

Yet another object of the invention is to provide a process which makesit possible to incorporate easily into the fibrous material of thegasket componentsinsuring greater elastic recovery of the compressedgasket.

in accordance with the invention, the process of manufacturing gasketscomprises the projection of a mixture containing at least 70 parts byweight of a filler material, which is preferably fibrous and atmost 30parts of a settable binding agent so as to form a thick layer on atleast one face of a support formed by a substantially flat sheet. Thesupport provided with this layer is then subjected to a compressionwhich reduces the thickness of this layer to less than one-tenth itsoriginal thickness, thus increasing its density at least 10 times. Thelayer is then treated to set the binding agent. The materials which maybe used in accordance with the invention may take the form of fibers,granules, powders, or small scales, and are selected from the groupconsisting of:'

Asbestos of the chrysotile crocidolite, or amosite type, the

fibers of which are less than mm long;

Natural cellulosic fibers such as those of manila or jute, or

synthetic fibers such as a polyamide, polyester, polyvinylchloride, orepoxy resin. These fibers may vary in length up to 30 mm;

Powdered cork grains which may range from 0.1 to 6 mm in diameter;

Metallic fibers from 3 to 30 mm in length;

The aforesaid materials are given purely by way of example but othersmay be used, such as powdered elastomers.

These materials may be used along or in mixtures with each other. Thus,for example, gaskets according to the invention may be carried out byusing mixtures of cellulosic fibers and polyamide fibers or mixtures ofcork granules and cellulosic fibers.

In accordance with the invention, any binding agents may be used whichare capable of being projected and which, after subsequenttransformation, are capable of insuring the cohesion of the gasketaccording to the invention. In one method of carrying out the invention,the binding agents are used in the form of solid powders or granuleswhich may be 'ad' vantageously mixed with the fibrous or granularmaterial during its projection onto the support. The cohesion of thebinding agent usually results from a subsequent heat treatment whichtakes place during or after the compression of the various productsprojected onto the support, and causes fusion or polymerization of thebinding agent.

Among the binding agents which may be used in accordance with theinvention are phenolic resins, urea formol resins, epoxy resins,polyester resins, vinyl resins, polyethylene resins, gelatin, orelastomers such as those obtained from acrylonitrile butadiene,silicones, or polychloroprene.

In accordance with the invention, an adhesive which serves solely tocause the various constituents to adhere to the support may, during theapplication of these constituents to the support, be in a state which iscapable of producing such adhesion.

In certain cases, the adhesive according to the invention may consist ofthe binding agent itself, for example when the latter is sprayedsimultaneously but independently of the fibrous, material, for examplein a solution or in a liquid state. This may also be true when thefibrous material mixed with the binding agent in the form of solidparticles is projected for example onto a support which has first beenheated in order to insure at least partial melting of the binding agentand thereby produce the desired adhesive effect.

Suitable adhesives for use in'accordance with the invention includesynthetic resins, such as vinyl resins, polyethylene, phenoplasticresins, aminoplastic resins, epoxy resins, polyester resins, and thepolyurethanes.

It is also possible to use adhesives having an elastomeric base such asnatural rubber or synthetic rubber (GRS, butadiene, acrylonitrile,polychloroprene, butyl, fluorocarbons, silicones, etc.

In all cases, the binding agent and adhesive must be selected independence upon the chemical nature of the materials to be projected soas to obtain the best final result. In accordance with the invention,the fibrous material and the binding agent whether particulate or notmay be projected while suspended in a gas through one spraying nozzle,while the adhesive is sprayed through another spray gun.

When necessary, the fibrous material, the binding agent, the

I adhesive, when not mixed together, may be projected through ferentlengths of time.

three separate spray guns onto the support. in. accordance with theinvention, various types of support may be used. These include sheetswhich have been perforated by stamping with punches, which leave sharpedges on opposite sides of the sheet, while imparting the appearance ofa rasp thereto.

It is also possible to use smooth sheets or even webs of a metallicmaterial or webs made from asbestos or synthetic fibers.

The thickness of the sheet or the cloth is less than onefourth of thethickness of the completed gasket.

According to a variation of the process according to the invention thematerial .may be projected against a support to which it does notadhere. The support is then eliminated after a step which causes thebinding agent to serve the function of the support.

The gaskets according to the invention may be manufactured by sprayingthe various products hereinbefore described onto continuous supportingstrips and then cutting the strips in an appropriate manner to producegaskets having the desired shapes.

The support may also be cut out first and the gasket produced in itsfinal form by projecting the particulate materiv This permits theproduction of mats of fibers the directions of which are, for example,crossed, which have been difficult to obtain economically in priormethods of manufacture.

The gaskets according to the invention may have different thicknesses atdifferent points. This characteristic may be easily produced by sprayingdifferent parts of the gasket for dif- This characteristic of gasketsaccording to the invention is very valuable because, as is well known,the technique of internal combustion engines is rapidly evolving towardthe use of light alloys for making engine blocks while the cylinderjackets continue to be made of cast iron.

These have different rates of expansion which make the manufacture ofcylinder head joints particularly difficult.

The gaskets according to the invention, which may be of differentthicknesses at different points, make it possible to solve this problemin a particularly satisfactory manner, since the variations in thethickness of the gasket may substantially correspond to departures fromflattness in the surfaces in contact with the gasket. U.S. Pat. ,No.2,753,199, already describes a metallic cylinder head gasket. Themetallic sheet forming the gasket is covered on its two surfaces with athin layer of a thermosetting resin to protect it against corrosion.This layer is covered with a thin layer of fibrous material, such asasbestos. The asbestos adheres to the layer of resin. According to thispatent it is already known to apply to a metallic gasket a layerconsisting of a mixture of thermosetting resins and a filler material.In view of the necessity to protect the metal against corrosion, thismixture comprises much more resin than fibrous material. It has beenfound that such coatings assist in the fonnation of a good seal.

These known processes, however, have certain disadvantages. In the firstplace the projection of a layer of fibers onto a subjacent layer offresh resin makes it impossible to produce a thick layer of fibrousmaterial because once the resinous layer is entirely covered withfibers, the fibers subsequently projected can no longer come in contactwith the resinous layer and are thus not secured thereto.

n the other hand, if a mixture consisting of a major part of resin, andcontaining fibers or a powdered filler material, is projected onto themetallic sheet, instead of applying it with a roller as is .known, it ispossible to obtain thick sufficiently dense layers.

However, when the portion of resins is diminished and the proportion offibrous or pulverulent materials is increased, the cohesion of the layerprojected diminishes very rapidly and the seal formed becomes quicklyunusable.

It follows that joints consisting principally of fibers or pulverulentmaterials with or without a thin internal metallic layer cannot beproduced by projection. Only coatings comprising a high proportion ofresinfor metallic gaskets may be made in this manner.

By projecting a mixture comprising at least 70 parts of filler material,for example asbestos fiber, and at most 30 parts of binder, against asupport, the inventor has found that he: is able to obtain a very thicklight layer having somewhat the appearance and consistency of freshsnow. Suprisingly, he has, found that this light layer can easily becompressed with practically no loss by outward flow along its edges sothat the material moves almost solely in the direction of compression,despite a compression which reduces the thickness of the layer to notmore than one-tenth and in general about one one-hundredth of itsoriginal thickness. In order to avoid such great compression, whichappears to cause difficulties especially when the layer projectedagainst the support is several centimeters thick, applicant hassuccessively projected several thinner layers one after the other,compressing each layer before projecting the next. It has been foundthat the different layers adhere very poorly to each other and thatsatisfactory gaskets cannot be made in this manner.

ln order that the invention may be better understood, several examplesthereof will now be described, purely by way of illustration andexample.

EXAMPLE I A cylinder head gasket according to the invention is made inthe following manner:

A mixture containing 90% by weight of chrysotile asbestos sold under thetrademark Grade SR" and by weight of phenoplastic resins sold; by theformer-.Plastugi] Company (now called the Plastimer Company) under thetrademark Phenorez 71" is mechanically mixed together. The resin has amelting point at about C.

This mixture is projected by a flocking gun perpendicularly against aperforated sheet of the rasp type having a thickness less than 0.5 mmand, for example, equal to 0.2 mm, which has been first spray-coatedwith 100 grams per square meter of a polyvinylacetate emulsion oncecalled Rhodopas 5425 and now sold under the trademark Rhodopas 5,000 SMRby the Rhone Poulenc Company, diluted in an equal volume of water.

550 grams per square meter of a mixture of asbestos and phenoplasticresins is projected against each face of the sheet in a single pass.This produces, on each face, a light layer having the appearance of asnow or foam about 6 cm thick.

It will be appreciated that, by using particles of very small dimensionsand spraying from a substantial height a high degree of homogeneityresults. Moreover, it is easy to control the constancy of the thicknesswith the naked eye or by means of appropriate apparatus. If too greatinequalities appear it is then easy to eliminate them, either by localleveling of the material or by adding supplementary material, and therewill then be no substantial lack of uniformity in the thickness of thegasket when it is completed.

Since the layers in the present example are compressed so as to have athickness of less than one one-hundredth their original thickness itwill be seen that it is thus possible to obtain gaskets having auniformity of thickness which cannot be obtained in the other knownprocesses.

The product obtained in this manner is then subjected to a pressure ofabout 200 bars, calendared to a thickness of 1.2 mm, and the resinstherein polymerized by heating them for about 15 minutes at atemperature of C.

The gasket is then cut to the desired shape with an appropriateapparatus.

In this example the layer has been compressed to less than oneone-hundredth of its original thickness without any substantialresulting lateral flow.

EXAMPLE 2 In order to produce a gasket according to the invention, amixture containing 80-95% by weight of asbestos of the crocidolite typeand 15-50% by weight of aminoplastic (ureaformol) resins sold by thePlastugil Company under the trademark Uralite are mechanically mixedtogether.

This mixture is then projected perpendicularly onto a perforated plate0.2 mm thick which has first been cut to the shape of the gasket andcoated with an epoxy varnish at the rate of 80 grams of varnish persquare meter.

The mixture is projected onto each face of the sheet at the rate of 600grams per square meter. The result is two layers, each a little morethan 6 cm thick.

The gasket is then positioned for 20 minutes inside a heating pressexerting a pressure of 200 bars at a temperature of 130 C. The thicknessof each layer then becomes 0.55 mm.

EXAMPLE 3 In order to produce a gasket according to the invention amixture is prepared which contains 70% by weight of cellulosic fibersknown as Manila Fibers having a length of 3-5 mm, 20% by weight ofpolyamide fibers having a length of 3-5 mm, and 10% by weight of epoxyfibers sold by the Van Cauvenberghe Company under the trademarkTritorga.

The mixture is projected perpendicularly againsta support consisting ofa sheet of glass which is impregnated with silicones so as to preventadhesion of the particles thereto.

This is subsequently compressed under a pressure of 60-80 bars for 10minutes at a temperature of C.

The sheet of glass is then removed and the gaskets are cut from thesheets obtained in this manner.

In each of the three foregoing examples 20 parts of elastomer particlesmay be mixed with the fibers to be projected. This results in thedispersal of the elastomer particles in the fibrous mass. Theseparticles nevertheless retain a certain degree of freedom which sufficesto pennit them to elastically deform thus improving the elastic recoveryof the gasket when it has been compressed. These elastomer particles mayhave any desired shape, but are preferably spherical.

EXAMPLE 4 A gasket according to the invention is produced by projectingasbestos of the chrysotile type sold under the trademark Grade 5R onto asmooth sheet which has first been coated with an acrylonitrile butadienerubber solution at the rate of 25 grams of rubber per square meter ofsheet.

On each face there is first applied a first layer of asbestos using aspray gun which is inclined at 35 to the surface of the sheet. A secondvery fine layer of a binding agent consisting of the same solution ofacrylonitrile butadiene rubber as the adhesive is then applied.

A second layer of asbestos is then projected at an angle of 145 to thesheet.

A number of successive projections of asbestos are made which vary independence on the thickness of the gasket which is to be produced. Theresulting product is then calendered and heated for minutes at atemperature of 130 C.

After this, the gasket is cut to the desired shape.

EXAMPLE 5 A perforated sheet is cut to the shape of the gasket desiredand then coated with 100 grams per square meter of an emulsion ofpolyvinylacetate sold under the trademark Rhodopas 5425, diluted with anequal volume of water.

A mixture consisting of 90% by weight of asbestos sold under thetrademark Grade 6D and 10% by weight of phenoplastic resins sold by thePlastugil Company under the trademark Phenorez 71 is then projected ontoeach face of this gasket.

A thicker deposit is made on some areas of the gasket than on others.The gasket is then compressed so as to give it a uniform thickness andcured at a temperature of 130 C for l5 minutes.

The result is a gasket which has zones of reduced compressibility whichcorrespond to the zones of greatest thickness and which are separated byzones which are more compressible and correspond to the zones of normalthickness.

EXAMPLE 6 A smooth metallic sheet which is coated with 60 grams persquare meter of a polyester varnish is cut to the shape of the desiredgasket.

A mixture consisting of 90% by weight of cellulosic fibers and 10% byweight of gelatin is then immediately projected onto each surface ofthis sheet.

The resulting product is placed in a heating press which compresses itfor 5 minutes at a temperature of 130 C under a pressure of 6080 bars.

A coat of polyester varnish is then applied to the areas of the gasketwhich are to be subjected to the greatest pressure.

A mixture consisting of 75% by weight of cork having granules which varyfrom 0.5 to 1 mm in diameter, and 25% by weight of gelatin, is thenprojected onto the gasket. The cork adheres only to those portions ofthe gasket which have received the polyester varnish. The resultinggasket is compressed in a heating press for 5 minutes at a temperatureof 100 C and a pressure of 10 bars.

This yields a gasket having zones which differ in thickness andcompressibility. I

When the particles to be projected are fibers, it is possible toadvantageously use the process of electrostatic flocking which makes itpossible to produce on the support fibers What is claimed is: l. Amethod of making gaskets comprising the steps of projecting inparticulate form on at least one surface of a support consisting of asubstantially flattened surface at least 70 parts by weight of a fillermaterial and at most 30 parts by weight of a heat settable binding agentto form a layer of low density, subjecting the support provided withthis layer to a compression which reduces its thickness by and therebyincreases its density by at least 10 times, and treating said layer byapplication of heat to set the binding agent. 1

2. Method of making gaskets of fibrous material comprising the steps ofprojecting against at least one face of a support having a substantiallyplane surface from 70-90 parts of fibers and from 10-30 parts of a heatsettable binding agent to form a thick layer of low density on saidsupport, subjecting the support to a compression reducing the thicknessof the sheet to not more than one one-hundredth of its originalthickness and thereby increasing its density by at least times, andtreating the said layer by application of heat to set the binding agent.

3. Method as claimed in claim 1 comprising the step of treating saidsurface with an adhesion preventing material before said particulatematerial is projected thereagainst, and removing said support after saidbinding agent has set.

4. Method as claimed in claim 2 in which the thickness of said supportis less than one-fourth that of the completed gasket.

5. Method as claimed in claim 1 comprising the step of applying anadhesive to a flat surface of said support.

6. Method as claimed in claim 2 in which the support is a perforatedsheet less than 0.5 mm thick.

7. Method as claimed in claim 2 in which said'layer is at least 5 cmthick.

8. Method as claimed in claim 1 in which said support is a cloth.

9. Method as claimed in claim 2 in which the material projected againstsaid surface comprises 20 parts of elastomeric particles.

10. Method as claimed in claim 1 in which said material is projected byelectro-static flocking.

11. Method as claimed in claim 1 in which said filler material comprisesfibers and said fibers are oriented in different directions in differentareas on the surface of said support.

12. Method as claimed in claim 1 in which the layer formed on saidsupport varies in thickness from one part of said support to another.

13. Method as claimed in claim 1, in which said heat settable bindingagent is selected from the group consisting of phenolic resins,urea-formol resins, epoxy resins, polyester resins, gelatin, andelastomers.

14. A method of making gaskets comprising the steps of projecting inparticulate form on at least one surface of a support consisting of asubstantially flattened surface at least 70 parts by weight of a fillermaterial and at most 30 parts by weight of a heat fusible binding agentto form a layer of low density, subjecting the support provided withthis layer to a compression which reduces its thickness by 90% andthereby increases its density by at least 10 times, and treating saidlayer by heat to cause fusion of said binding agent.

15. Method as claimed in claim 14, comprising the steps of projectingfrom 7090 parts of fibers and from 10-30 parts of binding agent, andsubjecting the support to a compression reducing the thickness of thesheet to not more than one onehundredth of its original thickness andthereby increasing its density by at least 100 times.

16. Method as claimed in claim 14, in which said binding agent isselected from the group consisting of vinyl resins and polyethyleneresins.

2. Method of making gaskets of fibrous material comprising the steps ofprojecting against at least one face of a support having a substantiallyplane surface from 70-90 parts of fibers and from 10-30 parts of a heatsettable binding agent to form a thick layer of low density on saidsupport, subjecting the support to a compression reducing the thicknessof the sheet to not more than one one-hundredth of its originalthickness and thereby increasing its density by at least 100 times, andtreating the said layer by application of heat to set the binding agent.3. Method as claimed in claim 1 comprising the step of treating saidsurface with an adhesion preventing material before said particulatematerial is projected thereagainst, and removing said support after saidbinding agent has set.
 4. Method as claimed in claim 2 in which thethickness of said support is less than one-fourth that of the completedgasket.
 5. Method as claimed in claim 1 comprising the step of applyingan adhesive to a flat surface of said support.
 6. Method as claimed inclaim 2 in which the support is a perforated sheet less than 0.5 mmthick.
 7. Method as claimed in claim 2 in which said layer is at least 5cm thick.
 8. Method as claimed in claim 1 in which said support is acloth.
 9. Method as claimed in claim 2 in which the material projectedagainst said surface comprises 20 parts of elastomeric particles. 10.Method as claimed in claim 1 in which said material is projected byelectro-static flocking.
 11. Method as claimed in claim 1 in which saidfiller material comprises fibers and said fibers are oriented indifferent directions in different areas on the surface of said support.12. Method as claimed in claim 1 in which the layer formed on saidsupport varies in thickness from one part of said support to another.13. Method as claimed in claim 1, in which said heat settable bindingagent is selected from the group consisting of phenolic resins,urea-formol resins, epoxy resins, polyester resins, gelatin, andelastomers.
 14. A method of making gaskets comprising the steps ofprojecting in particulate form on at least one surface of a supportconsistinG of a substantially flattened surface at least 70 parts byweight of a filler material and at most 30 parts by weight of a heatfusible binding agent to form a layer of low density, subjecting thesupport provided with this layer to a compression which reduces itsthickness by 90% and thereby increases its density by at least 10 times,and treating said layer by heat to cause fusion of said binding agent.15. Method as claimed in claim 14, comprising the steps of projectingfrom 70-90 parts of fibers and from 10-30 parts of binding agent, andsubjecting the support to a compression reducing the thickness of thesheet to not more than one one-hundredth of its original thickness andthereby increasing its density by at least 100 times.
 16. Method asclaimed in claim 14, in which said binding agent is selected from thegroup consisting of vinyl resins and polyethylene resins.